U.S. patent number 5,067,993 [Application Number 07/345,549] was granted by the patent office on 1991-11-26 for magnetic core material made of fe-co base alloy for high frequencies.
This patent grant is currently assigned to Mitsubishi Materials Corporation. Invention is credited to Saburo Wakita, Kiyoshi Yamaguchi, Norio Yanagisawa.
United States Patent |
5,067,993 |
Wakita , et al. |
November 26, 1991 |
Magnetic core material made of Fe-Co base alloy for high
frequencies
Abstract
A magnetic core material made of a Fe-Co base alloy for use at
high frequencies, and has excellent high-frequency alternating
magnetic properties. The core material composition is Co: 45-53% by
weight, C: 0.3-3% by weight, one or both of Mn and Si: 0.1-2% by
weight, at least one of Mg, Ca, and Ce: 0.1-0.2% by weight, and the
remainder Fe and unavoidable impurities. The structure of the alloy
comprises a ferrite matrix containing graphite in an amount of from
1-20% by volume dispersed therein. The material is applied, for
example, in a dot impact printer and to a pulse motor.
Inventors: |
Wakita; Saburo (Noda,
JP), Yamaguchi; Kiyoshi (Minamisaitama,
JP), Yanagisawa; Norio (Kitamoto, JP) |
Assignee: |
Mitsubishi Materials
Corporation (Tokyo, JP)
|
Family
ID: |
16515238 |
Appl.
No.: |
07/345,549 |
Filed: |
April 14, 1989 |
PCT
Filed: |
August 18, 1988 |
PCT No.: |
PCT/JP88/00817 |
371
Date: |
April 14, 1989 |
102(e)
Date: |
April 14, 1989 |
PCT
Pub. No.: |
WO89/01533 |
PCT
Pub. Date: |
February 23, 1989 |
Foreign Application Priority Data
|
|
|
|
|
Aug 19, 1987 [JP] |
|
|
62-205940 |
|
Current U.S.
Class: |
148/311; 148/308;
420/9; 420/117; 420/435; 148/306; 148/315; 420/99; 420/120;
420/581; 148/313 |
Current CPC
Class: |
H02K
1/02 (20130101); H01F 1/147 (20130101); C22C
38/10 (20130101) |
Current International
Class: |
C22C
38/10 (20060101); H02K 1/00 (20060101); H02K
1/02 (20060101); H01F 1/147 (20060101); H01F
1/12 (20060101); H01F 001/04 () |
Field of
Search: |
;148/306,307,308,311,313,315 ;420/9,99,117,120,435,581 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
53-108824 |
|
Sep 1979 |
|
JP |
|
62-227064 |
|
Oct 1987 |
|
JP |
|
63-11650 |
|
Jan 1988 |
|
JP |
|
571676 |
|
Sep 1945 |
|
GB |
|
Primary Examiner: Sheehan; John P.
Attorney, Agent or Firm: Frishauf, Holtz, Goodman &
Woodward
Claims
We claim:
1. A Fe-Co alloy magnetic core material for use with high frequency
signals comprising 45 to 53% by weight of Co, 0.3 to 3% by weight
of C, a total of 0.1 to 2% by weight of at least one selected from
the group consisting of Mn and Si, and the balance Fe and
unavoidable impurities, the structure of said alloy comprising a
ferrite matrix containing graphite in an amount of from 1 to 20% by
volume dispersed therein.
2. The magnetic core material of claim 1, wherein said Fe-Co alloy
contains 0.5 to 1.5% by weight of C.
3. The magnetic core material of claim 1, wherein said graphite is
spheroidal graphite having a mean diameter of from 0.5 to 50
.mu.m.
4. The magnetic core material of claim 1, wherein said graphite is
spheroidal graphite having a mean diameter of from 2 to 4
.mu.m.
5. The magnetic core material of claim 2, wherein said graphite is
spheroidal graphite having a mean diameter of from 2 to 4
.mu.m.
6. A Fe-Co alloy magnetic core material for use with high frequency
signals comprising 45 to 53% by weight of Co, 0.3 to 3% by weight
of C, a total of 0.1 to 2% by weight of at least one selected from
the group consisting of Mn and Si, a total of 0.01 to 0.2% by
weight of at least one selected from the group consisting of Mg, Ca
and Ce, and the balance Fe and unavoidable impurities, the
structure of said alloy comprising a ferrite matrix containing
spheroidal graphite in an amount of from 1 to 20% by volume
dispersed therein.
7. The magnetic core material of claim 6, wherein said Fe-Co alloy
contains 0.5 to 1.5% by weight of C.
8. The magnetic core material of claim 6, wherein said spheroidal
graphite having a mean diameter of from 0.5 to 50 .mu.m.
9. The magnetic core material of claim 6, wherein said spheroidal
graphite having a mean diameter of from 2 to 4 .mu.m.
10. The magnetic core material of claim 7, wherein said spheroidal
graphite having a mean diameter of from 2 to 4 .mu.m.
11. The magnetic core material of claim 6, which contains 45.5% Co,
1.00% C, 0.65% Mn and a trace amount of Mg.
12. The magnetic core material of claim 6, which contains 49.2% Co,
0.93% C, 0.74% Mn and a trace amount of Mg.
13. The magnetic core material of claim 6, which contains 52.7% Co,
1.11% C, 0.72% Mn and trace amount of Mg.
14. The magnetic core material of claim 6, which contains 49.4% Co,
0.34% C, 0.76% Mn and a trace amount of Ca.
15. The magnetic core material of claim 6, which contains 49.0% Co,
0.65% C, 0.80% Mn and a trace amount of Ce.
16. The magnetic core material of claim 1, which contains 48.6% Co,
1.04% C and 0.75% Mn.
17. The magnetic core material of claim 6, which contains 49.3%,
2.12% C, 0.72% Mn and a trace amount of Mg.
18. The magnetic core material of claim 6, which contains 48.7% Co,
2.88% C, 0.75% Mn and a trace amount of Mg.
19. The magnetic core material of claim 1, which contains 49.1% Co,
0.86% C and 0.12% Mn.
20. The magnetic core material of claim 6, which contains 49.2% Co,
0.93% C, 1.88% Mn and a trace amount of Ce.
21. The magnetic core material of claim 6, which contains 48.7% Co,
1.01% C, 0.58% Si and a trace amount of Mg.
22. The magnetic core material of claim 6, which contains 49.0% Co,
1.12% C, 0.70% Mn, 0.32% Si and a trace amount of Mg.
23. The magnetic core material of claim 6, which contains 48.4% Co,
0.97% C, 0.78% Mn and 0.02% Mg.
24. The magnetic core material of claim 6, which contains 49.1% Co,
0.90% C, 0.74% Mn and 0.08% Ca.
25. The magnetic core material of claim 6, which contains 48.3% Co,
0.92% C, 0.75% Mn and 0.18% Ce.
26. The magnetic core material of claim 6, which contains 48.6% Co,
0.96% C, 0.64% Si, 0.06% Mg and 0.02% Ca.
27. The magnetic core material of claim 6, which contains 49.0% Co,
1.01% C, 0.60% Mn, 0.55% Si, 0.04% Mg, 0.02% Ca and 0.03% Ce.
Description
BACKGROUND OF THE INVENTION
This invention relates to a magnetic core material made of Fe-Co
base alloy for use at high frequencies, and which has excellent
high-frequency alternating magnetic properties. The core material
is used in a head core and a plunger yoke of a dot impact printer,
and further in a stator and a rotor of a pulse motor.
Such a magnetic core material for use at high frequencies with high
frequency signals usually should have a characteristic that a
magnetic flux induced due to an applied current rises, and eddy
current losses due to an excess current are reduced by making a
current resistance ratio of the magnetic core large. Therefore,
most magnetic core materials are made of an Fe base casting alloy
and have a relatively large current resistance ratio, and excellent
magnetic properties. The materials have a composition of 2-3.5% by
weight Si and the remainder of Fe and unavoidable impurities.
Throughout the following, all percentages refer to weight
percentages.
Recently, a word processor, for example, needs to be small-sized
and to have high-performance. Therefore, a material of high
saturated magnetic flux density should be utilized for a head core
of a dot impact printer in order to form a compact head core. In
order to meet these requirements, attempts were made to use an
alloy of high magnetic flux density, e.g. 50% Fe-50% Co casting
alloy, instead of said Fe-Si casting alloy mentioned above (See
"Preliminary Lecture Paper of the 23rd autumn Meeting", Japan
Electric Material Technique Association). However, such an alloy of
high magnetic flux density has lower high-frequency magnetic
properties than one expects, partly because of a small current
resistance. A magnetic core material made of said Fe-Co alloy has a
poor magnetic flux rise because of a large eddy current loss.
Therefore, the magnetic core material made of the Fe-Co alloy
cannot meet the requirements of high-speed printing operations and
clarity of printing which are needed in a word processor.
SUMMARY OF THE INVENTION
An object of the present invention is to produce a magnetic core
material for use at high frequencies, and which has excellent
high-frequency alternating magnetic properties.
According to the present invention, a magnetic core material for
use with high frequency signals is made of a Fe-Co base alloy,
whose composition is 45-53% of Co, 0.3-3%, preferably 0.5-1.5% of
C, 0.1-2% of one or both of Mn and Si, 0.01-0.2% of at least one of
Mg, Ca, and Ce as needed, and the remainder of Fe and unavoidable
impurities, the structure of the alloy comprising a ferrite matrix
containing graphite in an amount of from 1-20% by volume dispersed
therein.
The magnetic core material of the present invention has better
high-frequency alternating magnetic properties than the
conventional magnetic core made of Fe-Co casting alloy, suffers
little eddy current loss, and gives improved magnetic flux rising.
Therefore, the magnetic core material of the present invention
readily meets the requirements of machines of high-speed,
small-size and high-performance.
The present invention was developed based on the above findings.
Below are descriptions as to the reasons for including ingredients
in the Fe-Co base alloy which forms a magnetic core material for
high frequency us according to the present invention, for limiting
ranges of ratios of the compositions included, and for limiting the
ratio of graphite as stated above. (a) Co
The reason for including Co as an ingredient is that Co together
with Fe in the specified amounts provides a solid solution of a
phase resulting in prominently high magnetic flux density. Also,
the reason for limiting the ratio of Co is that a desired high
magnetic flux density cannot be ensured when the ratio of Co is
less than 45% or more than 53%. Consequently, the amount of Co is
determined to be 45-53% in the present invention.
(b) C
The reason for including C as an ingredient is that most of the C
ingredient forms graphite which is dispersed in the ferrite matrix,
resulting in improvements in high-frequency alternating magnetic
properties. The reason for limiting the ratio of C is that when the
ratio is less than 0.3%, a volume ratio of graphite dispersed in
the matrix is less than 1% and the desired improvements in
high-frequency alternating magnetic properties cannot be ensured.
When the ratio of C is more than 3%, a volume ratio of graphite is
excessively more than 20% and high-frequency alternating magnetic
properties are inversely deteriorated. Consequently, the amount of
C is determined 0.3-3% in the present invention. Particularly,
0.5-1.5% is preferable in the present invention.
(c) Mn and Si
The reason for including these ingredients is that they show an
activity by deoxidation, resulting in improvements in
high-frequency alternating magnetic properties. The reason for
limiting the ratio of these ingredients as stated above is that a
desired deoxidation effect cannot be ensured when the ratio is less
than 0.1% while high-frequency alternating magnetic properties tend
to be deteriorated when the ratio is more than 2%. Consequently,
the ratio is thus determined to be 0.1-2% in the present
invention.
(d) Mg, Ca, and Ce
The reason for including these ingredients is that they dissolve
and become solute atoms in a ferrite matrix to improve a current
resistance of the matrix, resulting in improvement in
high-frequency alternating magnetic properties. These ingredients
further exhibit a degassing effect to reduce the ratios of both of
oxygen and nitrogen included in the alloy, resulting in improving
the high-frequency alternating magnetic properties. Therefore, if
better high-frequency alternating magnetic properties are required,
these ingredients are included as needed. The reason for limiting
the ratio of the ingredients as stated above is that when the ratio
is less than 0.01%, the desired effect due to said degassing
activity cannot be obtained, while if the ratio is more than 0.2%,
graphitization is difficult and also cementite (Fe.sub.3 C) is
crystallized, resulting in deterioration of the high-frequency
alternating magnetic properties. The ratio of these ingredients is
determined to be 0.01-0.2% in the present invention.
(e) A volume Ratio of Graphite
As described above, graphite dispersion in a ferrite matrix allows
prominent improvements in high-frequency alternating magnetic
properties. However, the desired improvements in high-frequency
alternating magnetic properties cannot be ensured when the volume
ratio of graphite is less than 1%, and also high-frequency
alternating magnetic properties inversely tend to be deteriorated
when the volume ratio is more than 20%. Consequently, the volume
ratio of graphite is determined to be 1-20% in the present
invention.
Also, although graphite of any shape improves the high-frequency
alternating magnetic properties, a comparison of, for example, a
spheroidal graphite with a flake graphite indicates that a magnetic
core material utilizing a spheroidal graphite shows better
high-frequency alternating magnetic properties than that utilizing
a flake graphite, under the condition that the amount of the
spheroidal graphite included is the same as that of a flake-shaped
graphite. The present inventors consider that this is because
spheroidal graphite more effectively suppresses the occurrence of a
eddy current. In order to improve the high-frequency alternating
magnetic properties, spheroidal graphite is preferably utilized in
a metal composition where a mean diameter of the spheroid is 0.5-50
.mu.m, and preferably 2-4 .mu.m.
Since a magnetic core material of the present invention for use at
high frequencies shows surprisingly excellent high-frequency
alternating magnetic properties, utilization of the magnetic core
in a head core material and a plunger yoke of a dot impact printer,
or in a stator and a rotor of a pulse motor shows excellent effects
and readily enables speeding-up of the operation of the dot impact
printer and the pulse motor, and therefore enables them to have
high-performance. Moreover, since the magnetic core material has
such a metal construction wherein graphite is dispersed therein, it
has better processibility than the conventional Fe-Co base alloy
which is likewise utilized in these applications.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a microphotograph at a magnification of 500 of a metal
composition (50%Fe-48.9%Co-1.1%C) of a magnetic core material made
of Fe-Co base alloy for use at high frequencies, showing one
example of the present invention.
FIG. 2 is a microphotograph at a magnification of 500 of a metal
construction (50%Fe-50%Co) of a conventional magnetic core material
made of Fe-Co base alloy for use at high frequencies.
DETAILED DESCRIPTION OF THE INVENTION
Next, a magnetic core material for use at high frequencies
according to the present invention will be described with reference
to the drawings.
By utilizing the conventional high frequency induction melting
furnace, a molten metal is prepared having a given composition and
then Mg, Ca, Ce, and Si (Si is provided as an alloy of Fe-Si) of
alloy compositions were totally or partly inoculated in the molten
metal, provided that when spheroidal graphite was to be formed, at
least one or more than two ingredients selected among Mg, Ca, and
Ce, and Fe-Si alloy were inoculated, and when flake graphite was
formed, Fe-Si alloy was inoculated. After inoculation, the molten
metal was cast to obtain a spheroidal graphite containing casting
and a flake graphite containing casting which has dot cores (for 9
pins of a dot impact printer) and which is used as a magnetic core
material for use at high frequencies. The spheroidal graphite
containing casting was sequentially kept at 850.degree. C. for 3
hours by utilizing a vacuum heating furnace and was 10 subjected to
annealing under the condition of furnace cooling. The flake
graphite containing casting was kept at 750.degree. C. for 2 hours
by utilizing a vacuum furnace, and was subjected to annealing under
the condition of furnace cooling. Consequently, each casting has a
structure wherein graphite is dispersed in a ferrite matrix.
Therefore, by processing the casting to form a finished shape, dot
core specimens 1-17 of the present invention made of Fe-Co base
alloy having ingredient ratios and a graphite ratio each of which
is respectively shown in Table 1 was formed.
Further, for a comparison, a molten metal having the same
composition ratio of comparative dot core specimens 1-5 as shown in
Table 1 was prepared, immediately cast and processed to form a
finished shape. The ratio of ingredients included in each of the
resulting dot cores 1-5 respectively departs from that according to
the present invention. The mark "*" in Table 1 shows a ratio
departing from that of the present invention.
Next, for each dot core as obtained above, two cores were contacted
wherein each end surface of each pin of the cores were exactly put
together by means of a non-magnetic medium of 0.3 mm thickness, and
a coil was wound around the pin of one dot core applied between the
coil terminals under the conditions: switching cycle: 50 Hz;
voltage between coil terminals: 30 V; switching time: 220 .mu.s;
and magnetomotive force (Ni): 150 ampere/turn (current x the number
of coil turns). The resulting magnetic flux .phi. induced in pins
of the dot core was measured in order to evaluate the
high-frequency alternating magnetic properties.
A pin of a dot core has a sectional rectangular shape of 9.6 mm in
length.times.0.17 cm.sup.2 in sectional area.times.2.3 mm in width.
A magnetic flux .phi. is measured by a search coil and calculated
by the following formula:
where Ns: the number of search coil turns (=3), and e: voltage
induced between search coils, utilizing a waveform analyzer. The
results are shown in Table 1. Table 1 also shows a volume ratio of
graphite dispersed in a matrix.
TABLE 1
__________________________________________________________________________
graphite magnetic ingredient composition % by weight Fe+ im- Volume
ratio flux .phi. (wb) specimen Co C Mn Si Mg Ca Ce purities shape
(%) (.times.10.sup.-6)
__________________________________________________________________________
dot cores 1 45.5 1.00 0.65 -- tr -- -- remainder sphe- 5.5 14.7 of
the roidal present 2 49.2 0.93 0.74 -- tr -- -- sphe- 5.2 16.4
invention roidal 3 52.7 1.11 0.72 -- tr -- -- sphe- 5.8 14.3 roidal
4 49.4 0.34 0.76 -- -- tr -- sphe- 1.3 13.8 roidal 5 49.0 0.65 0.80
-- -- -- tr sphe- 3.7 16.6 roidal 6 48.6 1.04 0.75 -- -- -- --
flake 5.1 13.7 7 49.3 2.12 0.72 -- tr -- -- sphe- 11.4 16.0 roidal
8 48.7 2.88 0.75 -- tr -- -- sphe- 18.6 13.8 roidal 9 49.1 0.86
0.12 -- -- -- -- flake 4.6 12.0 10 49.2 0.93 1.88 -- -- -- tr sphe-
5.3 12.7 roidal 11 48.7 1.01 0.58 tr -- -- sphe- 6.4 15.9 roidal 12
49.0 1.12 0.70 0.32 tr -- -- sphe- 6.5 16.8 roidal 13 48.4 0.97
0.78 -- 0.02 -- -- sphe- 6.2 17.0 roidal 14 49.1 0.90 0.74 -- --
0.08 -- sphe- 5.0 17.3 roidal 15 48.3 0.92 0.75 -- -- -- 0.18 sphe-
5.3 16.1 roidal 16 48.6 0.96 -- 0.64 0.06 0.02 -- sphe- 5.8 16.8
roidal 17 49.0 1.01 0.60 0.55 0.04 0.02 0.03 sphe- 5.8 17.5 roidal
comparative 1 43.1* 0.95 0.73 -- tr -- -- sphe- 5.4 8.9 dot cores
roidal 2 53.8* 1.02 0.70 -- tr -- -- sphe- 5.8 7.2 roidal 3 49.0
--* 0.65 -- -- -- -- -- -- * 6.6 4 48.7 0.21* 0.50 -- -- -- --
flake 0.8* 7.4 5 49.4 3.81* 0.60 -- -- -- -- flake 22.5* 7.7
__________________________________________________________________________
(*ratio which departs from that in the present invention)
From the results shown in Table 1, it is clear that all dot cores
1-17 of the present invention which have a composition wherein
spheroidal graphite or flake graphite are dispersed in a ferrite
matrix, show excellent high-frequency alternating magnetic
properties, while comparative dot cores 1-5 do not show sufficient
high-frequency alternating magnetic properties, even if only one
ratio of ingredients departs from that according to the present
invention (for C ingredient, a volume ratio of graphite also
departs from that according to the invention).
FIG. 1 is a microphotograph showing a metal composition of a
magnetic core material made of Fe-Co base alloy for use at high
frequencies in accordance with the present invention, and FIG. 2 is
a microphotograph showing a metal composition of a conventional
magnetic core material made of Fe-Co base alloy for use at high
frequencies. When comparing these microphotographs, it is found
that an alloy according to the present invention has graphite
dispersed therein, while a conventional alloy has no graphite
dispersed therein, in the absence of a carbon ingredient.
* * * * *